Gardenfors et al. proposed a metatheory for reasoning about rational ideal agents revision of beliefs. They provide a set of postulates and consequent theorems which characterize and constrain all revision algorithms. Since the primary thrust of most dynamic revision schemes are presently foundational in nature while the Gardenfors approach is based on coherence, we investigate these postulates as an alternative. In a microworld setting of blocks, actions are defined in terms of the basic Gardenfors operators of revision, expansion and contraction of theories. States of the blocks world are captured as canonical theories. Laws of the world are codified as the most entrenched formulas using the entrenchment relation of the Gardenfors postulates. It is thereby shown that linear planning is adequately handled. The equivalence of laws with pre- and post-conditions in the blocks world is suggested, and the need for strong ontology revision is shown for a modification of the microworld.